Methods of adjusting power spectral densities of telecommunications lines sending data are known, in particular for managing xDSL-type lines. As a general rule, a single adjustment device connected to the sender modem of each line is used to adjust certain parameters of each of the lines independently. For example, it is possible to set a required bit rate, a required minimum noise margin, the spectral power density, or parameters relating to error correction techniques.
The lines may have subscriptions to heterogeneous services that do not all require the same bit rate.
If the parameters of a line are insufficient to provide a service to which that line has a subscription, the adjustment device is used to adjust them to provide the service within the limit of the overall capacity of all the lines.
The parameters of a line are usually adjusted at the time of initializing a service on that line.
When the overall capacity is reached, some lines can no longer subscribe to a service, while others might have effective noise margins or effective bit rates that are much greater than the noise margins and bit rates required for the services to which they subscribe. The management of the xDSL lines as a whole is therefore less than the optimum.